Aircraft: MD80
Phase of flight: Descent
Anomaly: Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Other / Unknown

Our flying time was 1 hour 11 minutes. Aircraft MD-80; beverage service only in both cabins. The flight started out normally.The pilots were scheduled a meal. I served them when they were ready at cruise altitude; and shortly thereafter I retrieved their trays. I asked how much longer; and they said about 30 mins. (All of this happened about 25 minutes or less before landing. Some details are a bit fuzzy and I'm not sure if some details are out of order.)Flight Attendant #4 came up and we were chatting after the service; and she commented she was hearing some strange dings from the cockpit. I was not sure he was calling us; but I could hear them talking. The #4 Flight Attendant walked back to coach; and I put my ear to the cockpit door. At that moment I heard one of the pilots on the radio say 'we have lost all cabin pressure on the aircraft' (or something like that) I think; Oh; is that us? I think I had experienced a little ear popping. (I had just been through a bird strike 2 months earlier; and knew the pilots would be very busy for a few minutes) I decided on my own to (just in case) immediately prepare the cabin for landing- and did so. The worst that could happen would be that we were prepared early in case nothing happened. The flight attendants started picking up for landing. I immediately grabbed my tumbler insert and started grabbing glasses from passengers; no time for niceness! I dropped and broke one wine glass in the galley; picked up the biggest piece but left the rest. Flight Attendant #4 was mid-coach; she came up; and I whispered in her ear what I had overheard. I said; 'I am picked up; go back and finish coach'. Now we heard the 4 dings from the Captain. I'm not sure what he asked us- maybe about our ears popping. Flight Attendant #2 says there's a lot of ear popping and some people with ear pain. #4 is standing in front of me. Captain says we have a pressurization problem; that we will land in 15 minutes. (I signaled with my hands 15 minutes) Captain says he will drop the masks as a precautionary measure. (I think we were borderline altitude whether we needed them or not.) I told him the cabin was already picked up. (I'm not sure now if he said when on the ground we will assess conditions and get back to us.) I told the Captain the masks had not dropped. I immediately made a PA to the passengers and told them we had a pressurization problem; and when the masks drop; no smoking; make sure your seat belts are securely fastened; put the masks on; and continue using them until further notice. We do have a lot of ear popping now.I cleaned up the glass in the galley with safety cards just in case we have to evacuate; I don't want glass on the floor. The masks are still not down; I talked through the door and say that; then they drop. Everyone puts their masks on. I take my jumpseat; my mask does not drop. I think 'where's the little compartment with the pin hole?' I see it; reach up and start pushing on it; and it finally opens. The 2 masks fall; (mask hose is very long!) I put it on and think; 'Is it working?' I'm not getting much air. I feel just a little air; but not much. Do I have to pull like the passengers to trigger it; or will I pull it out of the wall if I pull too hard? I leaned forward to look at the passengers and to also look at lavatory; and thank goodness it's vacant. I see the Number 4 in the aisle checking passengers. I got up; opened up the Forward Entry storage space to retrieve the O2 walk-around bottle; checked my breathing; and its okay so I closed the compartment without getting it. I checked all of First Class and about 10 rows of coach; and everyone had their masks on. I could smell the 'heat' from the O2 cylinders while walking through the cabin. I went back to my seat and put my mask back on.The Captain called and asked how we were doing; and I heard Number 4 say that seats 32 AB O2 compartment didn't open. The Captain announced we are okay; and that O2 was not needed any longer. He also said that Crash and Rescue would meet the flight; and we would stop on the tarmac and assess our aircraft; and he would get back to us.I did not say to discontinue masks; but most passengers started taking them off. The aircraft got very cold. The Captain made an announcement to the passengers on our status. I could see that the passenger in 3E had a concerned look on her face. I signaled to her that the Captain had his O2 mask on while speaking as he sounds like Darth Vader. We landed without incident. The aircraft came to a complete stop; Crash and Rescue checked us out; and said we were okay. The Captain then made an announcement that they would follow us to the gate. Fire and Rescue personnel came onboard; checked with the Captain; and we deplaned normally. Some passengers commented that they weren't sure if this was an April Fools day trick.The Fire and Rescue personnel checked the O2 cylinders in the Passenger Service units; they were very hot; and the Number 4 Flight Attendant made an announcement about not touching the cylinders.What would I have done differently: I would have dinged the girls in the back and given them a heads up on the situation first before making the prepare for landing PA. (I didn't want to make a big to-do about something in case I was wrong.) I would have told passengers to help their seatmates. They all did anyway. (We had a blind man on this flight) I would have told them when to discontinue using the masks. (Oops) I should not [have] taken for granted that I was okay and checked the passengers without my O2 walk-around. (Even though I knew we were not that far from landing). I wish I was clearer about our jumpseat O2 masks. (Do we have that little black trigger pin like the passengers do?) An MD-80 Number 1 Flight Attendant sequentially describes the events in the cabin following an in-flight decompression and the confusion encountered with activating the jumpseat O2 masks.